1. Field of the Invention
The present invention relates to a gripper device for a transport vehicle that is provided on an OHT (overhead hoist transport) or other transport vehicles to convey an object, e.g., a FOUP (front opening unified pod), in a suspended state and serves to hold the object. The present invention also relates to a transport vehicle and an overhead hoist transport vehicle.
2. Description of the Related Art
A transport vehicle gripper device for holding an upper portion (e.g., a flange) of a FOUP or other objects with a pair of gripping parts that can be opened and closed is known (e.g., Japanese Laid-open Patent Publication No. 2001-294390). Japanese Laid-open Patent Publication No. 2001-294390, for example, discloses a gripper device in which a guide rail is fixed to a bottom surface (or an under surface) of a top panel portion and a gripping part is attached from below to each of a pair of guide blocks mounted to the guide rail. Each of the gripping parts includes a support plate, a finger support plate, and a finger, arranged in order from bottom to top.
Also known is an overhead hoist transport (OHT) vehicle (e.g., Japanese Laid-open Patent Publication No. 2006-298535 and Japanese Laid-open Patent Publication No. 2006-8354) having a hoist table that can be raised and lowered by a hoist drive section and a pair of chuck parts of the gripping parts provided on the hoist table. The chuck parts are arranged to grip an upper portion (e.g., a flange) of a FOUP or other objects. Regarding this kind of overhead hoist transport vehicle, various techniques have been proposed for preventing the conveyed object from vibrating while the vehicle is moving. Japanese Laid-open Patent Publication No. 2006-298535 presents a technique in which an elastic member is provided between the hoist drive section and the hoist table to prevent vibrations of the overhead hoist transport vehicle from being transmitted to the object. Japanese Laid-open Patent Publication No. 2006-8354 presents a technique in which a pressing means for pressing the object downward from above is provided on the hoist table, and the object is prevented from vibrating while the overhead hoist transport vehicle is moving by adjusting a height position of the hoist table and thereby adjusting a pressing force of the pressing means.
For example, in a conventional configuration disclosed in the above-mentioned Japanese Laid-open Patent Publication No. 2001-294390, the guide rail is provided on the bottom surface of the top panel portion, and the guide rail is commonly fixed to the bottom surface of the top panel portion with screws. However, such a conventional configuration has a technical problem in which, due to the weight of an object or vibrations occurring during conveyance of the object or the like, the screws may be damaged or loosened. Consequently, proper maintenance and repairs are required to prevent the object from falling. A reduction in the time and energy for such maintenance procedures is thus desired.
In addition, the above-mentioned conventional overhead hoist transport vehicle, for the purpose of lowering power consumption, commonly stops power feeding to a drive section such as a motor, which drives the pair of chuck parts of the gripping part, when the overhead hoist transport vehicle is conveying the object while gripping the object. When the power feeding to the drive section is stopped, gripping power of the pair of chuck parts decreases, which may result in the falling of the object. Consequently, the overhead hoist transport vehicle has a technical problem in which a device for preventing the object from falling, such as an opening preventing device for preventing the pair of chuck parts from opening, needs to be additionally provided on the gripping part. As a result, the weight of the gripping part would increase and the structure of the same would become complex, which results in a cost increase.